Thermally stable polyester fibers having inherent oil-stain release properties

ABSTRACT

Thermally stable fiber-forming polyesters having inherent oilstain release properties are produced from dicarboxylic acids, or reactive derivatives thereof, glycols and small amounts of mixtures of compounds having a typical general formula: R-O(GO)x-H, where R is an alkyl group containing an average of at least eight carbon atoms; G is a hydrocarbon radical selected from the group consisting of ethylene, propylene and isomers thereof, and mixtures of the above; and x has an average value at least equal to or greater than 9, and no greater than about 20.

D United States Patent 1151 3,669,935 King et a]. *June 13, 1972THERMALLY STABLE POLYESTER 56] References Cited FIBERS HAVING INHERENTOIL-STAIN UNITED STATES PATENTS RELEASE PROPERTIES 2,895,946 7/1959Huffman ..260/75 [72] Inventors; Hem-y L i Eugene Ringwald, both2,905,657 9/1959 Huffman 260/75 of Cary, James Randall, 3,033,824 5/1962Hufiman .260/75 lesville, Okla. 3,042,656 7/1962 Frey ..26O/77 3,223,75212/1965 Tate et al ..260/873 Asslgneer Monsanto Company, St LOUIS,2,556,295 6/1951 Pace et al .260/75 x 1 Notice: The portion of the termof this patent 3,461,468 8/1969 Morgan et a1. ..260/75 T 3 1:2 to June1989 has been dls Primary Examiner-Melvin Goldstein AttorneyThomas Y.Await, Jr., Robert L. Broad, J r., Neal E. [22] Filed: Nov. 6, 1969Willis and Elmer J. Fischer [21] Appl. No.: 874,638 [57] ABSTRACTRelated Application Data Thermally stable fiber-forming polyestershaving inherent oil- 63] continuatiomimpan of Ser No 789 528 Jan 7 stainrelease properties are produced from dicarboxylic acids, 1969 abandonedC ominuaiiomi'mpan of or reactive derivatives thereof, glycols and smallamounts of 824 6 Ma 1 3 '1969 mixtures of compounds having a typicalgeneral formula: R- y -O[GO],H, where R is an alkyl group containing anaverage of at least eight carbon atoms; G is a hydrocarbon CCIL,.260/7gbglDll7G/bg radical Selected from the g p consisting of ethylene58] Fie'ld g26O/77 propylene and isomers thereof, and mixtures of theabove; and

x has an average value at least equal to or greater than 9, and nogreater than about 20.

11 Claims, 6 Drawing Figures PATENTEDJUH 1 3 m2 SHEET 10F 3 8 6 4 2 OIQIm wMJOE 0x22 IO I NO. OF E o UNITS LOSS OF FORMALDEHYDE OF VARIOUS ETHYL ENE OXIDE POLYETHERS FIG. I.

N H N E T E R H O L A R E m M 2 3 ADDITIVE I NVEN TORS P'ATENTEDJUM 13m2 SHEET 2 UF 3 ll l 4208642086 2222 l l|| $3802 ll l2 l3 EXAMPLES M ZTTORN PATENTEDJUN 1 3 m2 3. 669.935

SHEET 30F 3 20 I 1 NO. OF CARBON ATOMS (R)= lz-Tols O O v v 5 1 5 O .1 Ja 3E LU L|.| E 5 g NO-OF ETHYLENE 2 o OXIDE UN|TS(X)=I2 0 IO 3o 0 IO 20NO. OF ETHYLENE OXIDE UNITSIX) NO. OF CARBON ATOMS IN ALKOXY GROUP (R)FIG.

I I5 2 O I I E E 5 FIG.

.gzvvrzrv'rozzs HENRY 1.. KING EUGENE 1.. RINGWALD JAMES c. RANDALL BY-%wym? ATTORN THERMALLY STABLE POLYESTER FIBERS HAVING INHERENTOIL-STAIN RELEASE PROPERTIES This is a continuation-in-part applicationof our co-pending applications Ser. No. 789,528, filed Jan. 7, 1969 andnow abandoned, and Ser. No. 824,092, filed May 13, 1969.

BACKGROUND OF THE INVENTION This invention relates to polyestersproduced by condensation reactions of polymethylene glycols anddicarboxylic acids or reactive derivatives thereof.

It is well known that some polymeric polyesters prepared by thecondensation of a glycol or its functional derivatives and adicarboxylic acid or a polyester-forming derivative thereof, such as anacid halide, a salt, or a simple ester of a dibasic acid and volatilemonohydric alcohol are excellent fiber-forming polymers. Commercially,highly polymeric polyesters are prepared, for example, by thecondensation of terephthalic acid or dimethyl terephthalate and a glycolcontaining from about two to ten carbon atoms. These polyesters arerelatively insoluble, chemically inactive, hydrophobic materials capableof being formed into filaments which can be cold-drawn to producetextile fibers of superior strength and pliability. However, it iswell-known that these materials are highly susceptible to oil staining,and once stained with an oil-type stain, are extremely difficult if notimpossible to restore to an unstained condition.

Unmodified polyesters are presently being treated externally withfinishes and the like in order to provide a measure of oil-stainresistance and oil release. Unfortunately, these finishes are expensiveto apply, and being applied externally, are, as a general rule, easilyremoved by washing.

SUMMARY OF THE INVENTION It is an object of this invention to provide aprocess for preparing synthetic linear condensation polyesters suitablefor production of filaments, fibers, fabrics, and the like which havethe inherent permanent capability of releasing oil-type stains withoutsacrificing the inherent heat stability of unmodified polyesters.

It is yet another object of this invention to provide a cha.interminating agent suitable for the production of synthetic linearcondensation polyesters for use in the production of filaments, fibers,fabrics, and the like which have inherent permanent oil-type stainreleasing characteristics, and thermal stability in the presence of air.

Briefly, the objects of this invention are accomplished by preparing afiber-forming polyester from a dicarboxylic acid and a glycol andcontaining in the polymer a small amount of compounds having a typicalgeneral formula: RO[G O] ,H, where R is an alkyl group containing anaverage of at least eight carbon atoms, G is a hydrocarbon radicalselected from the group consisting of ethylene, propylene and isomersthereof, and mixtures of the above; and x has an average value equal toor greater than 9, and no greater than about 20. Mixtures of thesecompounds may also be used. The additive may be used at concentrationsof from about 0.25 mole percent to about 3 mole percent based on themoles of the dibasic acid or derivative employed (the upper limit beingdictated primarily by processability considerations) with a preferredmole per cent concentration of from about 0.75 using the highermolecular weight compounds, to about 2.0 when using the lower molecularweight compounds.

The use of alkoxy polyethylene glycols to modify polyesters, as taught,for example, in US. Pat. No. 2,905,657, was seen to increase thedyeability of these polyesters, at the same time sacrificing heatstability, and with no apparent effect on the capability of fibers,filaments and fabrics produced from these polyesters to resist andrelease oily stains.

The modified polyester compositions of this invention are prepared byreacting an aromatic dicarboxylic acid, the polymethylene glycol and asmall amount of the alkoxy glycol additive under polyesterificationconditions until a fiber-form ing polymeric polyester composition isobtained. Small amounts of a chain-branching agent may also be added tothe reaction as desired.

The modified polyester compositions of the present invention are usefulin the production of shaped articles by extrusion, molding, or castingin the nature of yarns, fabrics, films, pellicles, bearings, ornaments,or the like. They are particularly useful in the production of thermallystable textile fibers having improved dyeability, particularly withdisperse dye.

To further understand the invention, reference will be made to theattached drawing that forms a part of the present application.

FIG. 1 is a graph showing the amount of formaldehyde loss at C. for 60minutes of alkoxy polyethylene glycols varying in the number of ethyleneoxide units present in the molecules;

FIG. 2 is a graph showing the amounts of mineral oil retained on samplesof fabric produced in accordance with this invention using variousamounts (in terms of weight based on the weight of the polymer) of atypical alkoxy polyethylene glycol (a reaction product of 14 molarequivalents of ethylene oxide with an approximately equimolar mixture ofstraight chain alcohols having 14-15 carbon atoms), the fabric havingbeen saturated with mineral oil, and subsequently washed with a standarddetergent and rinsed; all as described below for testing of oil-stainrelease characteristics;

FIG. 3 is a bar graph showing varying amounts of mineral oil percento.w.f.) retained on similar fabric samples using the same weight percentof various alkoxy polyethylene glycol chain terminators;

FIG. 4 is a graph showing the effect of increases of the number ofethylene oxide units (x) on mineral oil stain retention where the numberof carbon atoms in the alkyl group (R) of the alkoxy polyethylene glycolis held constant at from 12-15, the amount of the alkoxy polyethyleneglycol being used in each case being 5 percent by weight based on thepolymer;

FIG. 5 is a graph showing the effect in terms of mineral oil retention(percent o.w.f.) of changes in the number of carbon atoms in the alkylgroup (R) of the alkoxy polyethylene glycol, where the number ofethylene oxide units (x) was held constant at about 12; and

FIG. 6 is a graph showing the relationship of the ratio of ethyleneoxide units (x) to the number of carbon atoms in the alkyl group (R) ofthe alkoxy polyethylene glycol, in terms of mineral oil retention(percent o.w.f.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The synthetic linearcondensation polyesters contemplated in the practice of the inventionare those formed from dicarboxylic acids and glycols, and copolyestersor modifications of these polyesters and copolyesters. In a highlypolymerized condition, these polyesters and copolyesters can be formedinto filaments and the like and subsequently oriented permanently bydrawing. Among the polyesters and copolyesters specifically useful inthe instant invention are those resulting from heating one or more ofthe glycols of the series l-IO(CH ),.Ol-I, in which n" is an integerfrom 2 to 10, or cycloaliphatic glycols, with one or more dicarboxylicacids or ester-forming derivatives thereof. Among the dicarboxylic acidsand ester-forming derivatives thereof useful in the present inventionthere may be named terephthalic acid, isophthalic acid,p,p'-dicarboxybiphenyl, p,p'-dicarboxydiphenylsulfone,p,p'-dicarboxydiphenylmethane, and the aliphatic, cycloaliphatic, andaryl esters and half-esters, ammonium and amine salts, and the acidhalides of the abovenamed compounds, and the like. Examples of thepolyhydric alcohols which may be employed in practicing the instantinvention are ethylene glycol, trimethylene glycol, and tetramethyleneglycol, cyclohexane dimethanol, and the like. Polyethyleneterephthalate, however, is the preferred polymer because of the readyavailability of terephthalic acid or dimethyl terephthalate and ethyleneglycol, from which it is made. It also has a relatively high meltingpoint of about 250 through 265 C., and this property is particularlydesirable in the manufacture of filaments in the textile industry.

The additives which are an essential part of this invention arecompounds having a typical general formula: RO[G O] ,H, where R is analkyl group containing an average of at least eight carbon atoms; G is ahydrocarbon radical selected from the group consisting of ethylene,propylene and isomers thereof, and mixtures of the above; and x has anaverage value equal to or greater than 9, and no greater than about 20.By average is meant that the alkoxy glycol additive may comprisemixtures of the alkoxy glycol with some variances from the figuresshown; but that the average of the integers in the mixture will be asindicated. Preferably, the R group contains 12-16 carbon atoms. As thedegree of polymerization (x) increases, so does the inherent capabilityof resisting and releasing oil-type stains in a fabric prepared from theester. The additive may be used at concentrations of from about 0.25 to3 mole percent based on the moles of the dibasic acid or derivative witha preferred mole percent concentration of from about 0.75, using thehigher molecular weight compounds, to about 2.0, using the lowermolecular weight compounds.

Autoxidation is the phenomenon which is responsible for much of ourenvironmental chemistry. it is involved in the ageing of fats and oils,drying of paints, and degradation of natural and synthetic fibers. Theprocesses involved may be catalyzed by heat or light and are freeradical by nature. Generally speaking, autoxidation proceeds by freeradical, chain mechanisms; peroxy radicals and hydroperoxide groups areformed which are precursors to other products. Typical products fromautoxidation processes are alcohols and carbonyl-containing compounds.Chain-terminating reactions significantly affect the rates ofautoxidation processes.

The products observed from the autoxidation of alkoxy polyethyleneglycols are principally alcohol and formate ester chain-terminal groupsand formaldehyde, carbon dioxide, and water. Formaldehyde is a majorvolatile product. As above stated, significant and surprisingdifferences in thermal stability in the presence of oxygen have beenobserved among the various alkoxy polyethylene glycols. The type ofalkoxy unit and the degree of polymerization are apparently related tothe susceptibility of autoxidation.

It has been found, for example, that as the number of carbon atoms inthe alkoxy end group (R) is increased beyond the methoxy (with degree ofpolymerization held constant) there is a surprising decrease in theamount of formaldehyde evolved when the glycol additive is heated in asweep of air at 193 C., until the alkoxy group reaches eight carbonatoms, after which there is a leveling off. Further increase beyond 8-14carbon atoms in the alkoxy group causes no appreciable difference in theheat stability of the glycol. Exemplifying the above, alkoxy-terminatedpolyethylene glycol polymers having the structural formula: R(OCl-l CH-OH, were subjected to the above-described conditions, and liberatedformaldehyde in accordance with the following table.

*Alkoxy glycol prepared from mixture of 14 and 15 carbon alcohols.

It was also discovered that when these same alkoxy glycols were used aschain terminators in the production of modified polyesters, the heatstability effect was carried over to the polyester fiber.

On the other hand, where the number of carbon atoms in the alkoxy endgroup was held constant at about 14 and the degree of polymerization ofthe polyether chain was increased, the compounds being heated in a sweepof air at C., for 60 minutes, there was a marked increase in the numberof micro-moles of formaldehyde released as the degree of polymerization(number of ethylene oxide units) was increased from about 5 to 30,indicating a decrease in heat stability of the alkoxy glycol as shown byFIG. 1. Therefore, so far as heat stability alone is concerned, itappears that an alkoxy poly(oxyall ylene) glycol as described abovewhere R is an alkyl group containing no less than eight carbon atoms,and with an extremely low degree of polymerization would be optimum.

As shown in FIG. 3 (the compound structure being described underexamples 3-13), however, a degree of polymerization (x) of 9 isminimally optimum so far as comparative oil stain release properties areconcerned. Much more preferrable are the alkoxy poly(oxyalkylene)glycols with a degree of polymerization of 12 or more from thestandpoint of oil stain retention and release.

FIGS. 4, 5 and 6 illustrate that although the degree of polymerization(x) is the most significant single factor in characterizing the alkoxypoly(oxyalkylene) glycols in terms of oil stain release, especially goodresults are obtained where the ratio of ethylene oxide units (x) to thenumber of carbon atoms in the alkyl group (R) is about equal to orgreater than one. This is not to say that satisfactory oil stain releasequalities may not be obtained unless the ratio of x to R is about equalto or greater than 1; for commercially acceptable inherent oil stainrelease qualities (under 10 percent of retention) may be obtained wherethe ratio is less than 1 (see examples 7 and 9); however, forexceptionally fine oil-stain release qualities (3 percent retention orless based on the testing described) this ratio applies.

A minimum optimum value of 8 representing the number of carbon atoms inthe alkoxy end group has thus been established on the basis of heatstability, and a minimum optimum value of 9 as a degree ofpolymerization, has been established on the basis of oil stain retentionand release characteristics, recognizing that as the degree ofpolymerization is increased, there is a corresponding decrease in heatstability, with 1 =20 being maximally acceptable.

The precise structure of G is not considered critical in the instantinvention except insofar as it must exclude the alkoxy(polyoxymethylene)glycols which depolymerize under polyester polymerization conditions. Wehave found that the alkoxy poly(oxyethylene) and alkoxypoly(oxypropylene) glycols (including copolymers and block copolymers)and mixtures thereof produce good results in accordance with thisinvention.

The above can be partially explained in terms of inhibition of furtherautoxidation by products formed from the terminal alkoxy group in theinitial stage of oxidation. Those derived from short alkyl chains arevolatile at the test temperature, and escape without acting asinhibitors.

When the additive contains an alkoxy group which is an effectiveinhibitor of autoxidation, the number of alkyleneoxy units in thepolyether additive becomes significant. It has been found that chainshaving more than about 25 units are not adequately stable. This isbelieved to result from the low concentration of the inhibiting terminalalkoxy group in such a chain. On the other hand, a low number ofalkyleneoxy units per molecule results in an excessive number of chainterminations when an adequate weight of the modifier is added to achievethe desired oil-stain release characteristics. Poor processabilityresults from excessive chain termination.

If desired, the modified polyesters of this invention may containchain-branching agents, which, as taught in US. Pat.

No. 2,895,946, are employed to increase the viscosity of molecularweight of the polyesters, such as polyols which have a functionalitygreater than 2, that is, they contain more than two function groups,such as hydroxyl. Examples of suitable compounds are pentaerythritol;compounds having the formula: R-(OI-I), wherein R is an alkylene groupcontaining from three to six carbon atoms and n is an integer from 3 to6, for example, glycerols, sorbitol, l,2,6-hexanetriol and the like;compounds having the formula: R-(CI-hOl-I) wherein R is an alkyl groupcontaining from two to six carbon atoms, for example, trimethylolethane, trimethylol propane, and the like compounds up to trimethylolhexane; and the compounds having the formula:

(CH2)nOH] L L wherein n is an integer from 1 to 6. As examples ofcompounds having the above formula, there may be names 1,3,5-trimethylol benzene, 1,3,5-triethylol benzene; 1,3,5- tripropylolbenzene, l,3,5tributylol benzene; and the like.

Aromatic polyfunctional acids or their esters may also be employed inthis invention as chain-branching agents, and particularly those havingthe formula:

wherein R is H or an alkyl group containing one to three carbon atomsand x is an integer of 3 or 4. As examples of compounds having the aboveformula, there may be named trimesic acid, trimethyl trimesate, andtetramethyl pyromellitate, and the like. In addition, there may beemployed mixtures of the above acids and esters which are obtained inpractical synthesis. That is, in most instances, when preparing any ofthe compounds having the above formula, other related compounds havingthe same formula may be present in small amounts as impurities. Thisdoes not affect the compound as a chain-branching agent in thepreparation of the modified polyesters and copolyesters describedherein.

The chain-branching agents may be employed in the preparation of thepolyesters and copolyesters in amounts ranging from 0 to 0.7 molepercent, based on the amount of dicarboxylic acid or ester-formingderivative thereof employed in the reaction mixture. If thechain-branching agent is tetra-functional, as for example,pentaerythritol, quantities not in excess of 0.45 mole percent should beused. The preferred concentration of a tetra-functional chain-branchingagent is about 0.2 mole percent. If a tri-functional chainbranchingagent, such as for example, trimesic acid, is used, somewhat more isrequired for results equivalent to that of the tetra-functionalchain-branching agent, and amounts up to 0.7 mole percent may be used.The preferred concentration of a tri-functional chain-branching agent is0.5 mole percent.

In the practice of the present invention, the dibasic acid orester-forming derivative thereof, the glycol, and the alkoxypolyoxyalkylene glycol are charged to the reaction vessel at thebeginning of the first stage of the esterification reaction, and thereaction proceeds as in any well-known esterification polymerization. Ifdesired, the chain-branching agent may also be charged to the reactionvessel at this time.

When preparing the polyester from an ester, such as dimethylterephthalate, the first stage of reaction may be carried out at l70to180 C. and at a pressure ofO to 7 p.s.i.g. If the polyester is preparedfrom the acid, such as terephthalic acid, the first stage of reactionmay be carried out at about 220 to 260 C. and at pressures of fromatmospheric to about 60 p.s.i. g. The methanol or water evolved duringthe first stage of reaction is continuously removed by distillation. Atthe completion of the first stage, the excess glycol, if any, isdistilled off prior to entering the second stage of the reaction.

In the second or polymerization stage, the reaction may be conducted atreduced pressures and preferably in the presence of an inert gas, suchas nitrogen blanket over the reactants, the blanket containing less than0.003 percent oxygen. For optimum results, a pressure within the rangeof less than 1 mm. up to 5 mm. of mercury is employed. This reducedpressure is necessary to remove the free ethylene glycol that is formedduring this stage of the reaction, the ethylene glycol being volatilizedunder these conditions and removed from the system. The polymerizationstep is conducted at a temperature in the range of 220 to 300C. Thisstage of the reaction may be effected either in the liquid melt or solidphase. In the liquid phase, particularly, reduced pressures must beemployed in order to remove the free ethylene glycol which emerges fromthe polymer as a result of the condensation reaction.

Although the process of this invention may be conducted stepwise, it isparticularly adaptable for use in the continuous product of polyesters.In the preparation of the described polyesters, the first stage of thereaction takes place in approximately %to 2 hours. The use of anester-interchange catalyst is desirable when starting with dimethylterephthalate. In the absence of a catalyst, times up to 6 hours may benecesary in order to complete this phase of the reaction. In thepolymerization stage, a reaction time of approximately 1 to 4 hours maybe employed with a time of l to 3 hours being the optimum, depending oncatalyst concentration, temperature, viscosity desired, and the like.

The linear condensation polyesters, produced in accordance with thepresent invention, have specific viscosities in the order of about 0.25to 0.6, which represent the fiberand filament-forming polymers. It is tobe understood, of course, that nonfiber-forming polyesters may beproduced by means of the present invention, which have a greater or lessmelt viscosity than that s ecified above.

Specific viscosity, as employed herein, is represented by the formula:

Time of flow of the solvent in seconds 1 Viscosity determinations of thepolymer solutions and solvent are made by allowing said solutions andsolvent to flow by force of gravity at about 25 C. through a capillaryviscosity tube. In all determinations of the polymer solutionviscosities, a solution containing 0.5 percent by weight of the polymerdissolved in a solvent mixture containing 2 parts by weight of phenoland 1 part by weight of 2,4,6-trichlorophenol, based on the total weightof the mixture is employed.

The polyesters of this invention may be produced to form filaments andfilms by melt-spinning methods and can be extruded or drawn in themolten state to yield products that can be subsequently cold-drawn tothe extent of several hundred percent of their original lengths, wherebymolecularly oriented structures of high tenacity may be obtained. Thecondensation product can be cooled and comminuted followed by subsequentremelting and processing to fonn filaments, films, molded articles, andthe like.

Alternatively, the polyesters of this invention may be processed toshaped objects by the wet-spinning method, wherein the polyesters aredissolved in a suitable solvent and the resulting solution is extrudedthrough a spinnerette into a bath composed of a liquid that will extractthe solvent from the solution. As a result of this extraction, thepolyester is coagulated into filamentary material. The coagulatedmaterial is withdrawn from the bath and is then generally subjected to astretching operation in order to increase the tenacity and to inducemolecular orientation therein. Other treating and processing steps maybe given the oriented filaments.

If it is desired to produce shaped articles from the polyesters of thepresent invention which have a modified appearance or modifiedproperties, various agents may be added to the polyester prior to thefabrication of the articles or those agents may be incorporated with theinitial reactants. Such added agents might be plasticizers, antistaticagents, fire-retarding agents, stabilizers, and the like.

To further illustrate the present invention and the advantages thereof,the following specific examples are given, it being understood thatthese are merely intended to be illustrative and not limitative. Unlessotherwise indicated, all parts and percents are by weight.

The following procedure was used to prepare the: polymers in theexamples. The charge was added directly to a standard polyesterautoclave and the system was purged six times with nitrogen, allowingthe pressure to rise to 150 p.s.i.g., and then releasing it slowly toatmospheric pressure each time. Heat was then applied to the closedsystem, and when the temperature inside the autoclave had reached 100 to125 C., the stirrer was started. When the temperature of the outsidewall of the autoclave had reached about 250 C. (the inside temperaturebeing about 230 C. to 235 C. and the pressure being about 25 p.s.i.g.),the off-vapor valve was adjusted to maintain these conditions oftemperature and pressure. As the first distillate containing water andsome ethylene glycol appeared, the esterification stage was consideredto have started. The stirrer speed was set at 240 rpm. Thisesterification step usually took from about 40 to 60 minutes forcompletion, after which the pressure of the system was adjusted toatmospheric pressure. The heating rate was then increased until thetemperature reached about 280C. During this time, excess ethylene glycolwas distilled off. An ethylene glycol slurry of titanium dioxide wasintroduced through an injection port when the inside temperature hadreached about 260to 265C. Then the inside temperature was raised toabout 280 C. the pressure was maintained at less than 2 mm. Hg. and thepolymerization continued until a polymer having a specific viscosity inthe fiber-forming range between 0.30 to less than about 0.4 was formed.The polymer was extruded through a spinnerette, and the filamentsobtained were drawn about 5 times their original length over a hot pinat about 80C.

The oil stain retention and release tests used throughout the exampleswere based on mineral oil retention on a fabric prepared from a 50/10continuous filament prepared in accordance with this invention and pliedthree times into a 150/30 knitting yam, thereafter knitted with aYO-gauge knitting head at 86 courses per inch and 36 wales per inch.Rectangular sample fabric swatches from 6-12 grams were cleaned byextraction for four hours with methanol; then by a 4-hour extractionwith hexane. They were each stained with mineral oil by tumbling in ajar of Squibb" heavy liquid petroleum for 4 hours. A fresh aliquot ofthe oil was used for each staining. After tumbling, excess mineral oilwas removed from the swatch samples by padding on a ButterworthLaboratory Padder. Two passes through the rollers at 50 pounds pressurewere made. The first pass removed most of the oil. On the second pass,the swatches were sandwiched between paper towels to remove residual oilbetween fibers. This technique provided a fairly uniform pick-up on allsamples averaging about 21 percent based on the weight of the fiber.Fabric samples were laundered in a Kenmore laboratory washer (CatalogueNo. 3057340) for minutes followed by two rinse cycles of 10 minuteseach. lnitial water temperature was 160 F. for both washing and rinsing.Concentration of detergent was 1 gram/liter. The detergent used was astandard commercial detergent, Tide (XK). The liquor-to-fabric ratio wasapproximately 135:1. Fabric samples were then tumbled dry in a Sears(Lady Kenmore) dryer with the dryness contro set on 4. Fabric sampleswere then extracted with hexane for about 2 hours and the hexaneextracts were evaporated in aluminum cups. The residual percent mineraloil based on the weight of the fibers was determined by the weight ofthe mineral oil remaining in the cups. Each fabric sample was testedfive times, the average thereof being shown on FIGS. 2 and 3.Consecutive use of the samples, as described, indicate that oilretention and release qualities are not afiected by continuous washing.As used herein, the word permanent" describes a quality resistant toeffects of wash and wear and retained so long as the structuralintegrity of the fibers, filaments, etc. is maintained.

During the processing of polyester filaments, staple, blends, fabric,and the like, heating at various temperatures for various periods oftime is often necessary, e.g., polyester fabrics may be subjected totemperatures of 175 C. or higher for periods up to 10 minutes or more.The following thermal stability test was run where indicated: A S-gramsample of the polyester was fluffed into a ball, placed in an aluminumcup into which about 10 l-inch holes had been punched, and the ball washeated for 10 minutes at 175 C. in a circulating-air oven, with athermo-couple held at the center of the ball.

EXAMPLE 1 The autoclave was charged with 166 grams of terephthalic acid,400 ml. of ethylene glycol, 0.078 gram of lithium sulfate, 0.967 gram ofantimony trioxide, 0.20 gram of pentaerythritol; and 10 grams ofmethoxypolyethylene glycol having an average molecular weight of about550. Polymer and fiber were prepared following the procedure describedabove.

The fiber fused severely when heated at 175 C. for 10 minutes, thetherrno-couple within the carded ball recording a temperature of 220 C.

EXAMPLE 2 The autoclave was charged with grams terephthalic acid, 330ml. ethylene glycol, 0.04 gram lithium acetate, 0.1 gram antimonyglycoloxide, 0.2 gram pentaerythritol, and 10 grams of the reactionproduct of 14 molar equivalents of ethylene oxide with an approximatelyequimolar mixture of straight chain alcohols having 14-15 carbon atoms.Polymer and fiber were prepared following the procedure described inexample 1. The sample was tested for heat stability and resisted fusionwhen heated at C. for 10 minutes. When tested for oil stain retentionand release, the sample was found to have retained less than 5 percentbased on the weight of the fiber, of the mineral oil.

EXAMPLES 3-l 3 The autoclave was charged with 165 grams terephthalicacid, 330 ml. ethylene glycol, 0.04 gram lithium acetate, 0.1 gramantimony glycoloxide, 0.3 gram pentaerythritol, and 10 grams (5 percentby weight based on the polymer) of the following chain-terminatingcompounds:

Compound Structure where R is an alkyl radical having the number ofcarbon atoms indicated.

Fabric samples were prepared for oil stain retention and release asdescribed above; and the results of the mineral oil retention andrelease testing are illustrated by FIG. 3.

We claim:

1. A fiber-forming thermally stable synthetic linear condensationpolyester consisting of at least 85% by weight of an ester of a glycolselected from HO(CH ),,OH, in which n is an integer from 2 to 10, andcyclohexanedimethanol and terephthalic acid, modified with about 0.25 to3.0 mole percent based on the weight of terephthalic acid of achain-terminating additive having a general formula: R[GO] H, where R isan alkyl group containing at least eight carbon atoms; G is ahydrocarbon radical selected from the group consisting of ethylene, andpropylene, and x is an integer having a value at least equal to orgreater than 9, and no greater than about 20; said polyester havinginherent permanent oil stain release characteristics when in fiber form.

2. The composition of matter described in claim 1 wherein R is an alkylgroup containing an average of 12 carbon atoms and .x 20.

3. The new composition of matter described in claim 1 wherein R is analkyl group containing an average of eight carbon atoms andx= l2.

4. The new composition of matter described in claim 1 wherein R is analkyl group containing an average of l4-15 carbon atoms and x 14.

5. The new composition of matter described in claim 1 wherein saidadditive is present in an amount of about O.75-2.0 mole percent.

6. The new composition of matter described in claim 1 wherein thesynthetic linear condensation polyester is the polyester of terephthalicacid and ethylene glycol, and further modified with up to about 0.45mole percent, based on the amount of terephthalic acid, of atetra-functional chainbranching agent.

7. The new composition of matter defined in claim 6 wherein thechain-branching agent is pentaerythritol.

8. The new composition of matter described in claim 1 wherein thesynthetic linear condensation polyester is the polyester of terephthalicacid and ethylene glycol, and further modified with up to about 0.7 molepercent, based on the moles of the repeating unit of said polyester, ofa tri-functional chain-branching agent.

9. The new composition of matter defined in claim 8 wherein thechain-branching agent is trimesic acid.

10. The new composition of matter defined in claim 6 wherein thechain-branching agent is pentaerythritol, in an amount of about 0.2 molepercent, based on the weight of terephthalic acid.

11. The new composition of matter defined in claim 8 wherein thechain-branching agent is trimesic acid in an amount of about 0.5 molepercent based on the weight of the terephthalic acid.

2. The composition of matter described in claim 1 wherein R is an alkylgroup containing an average of 12 carbon atoms and x
 20. 3. The newcomposition of matter described in claim 1 wherein R is an alkyl groupcontaining an average of eight carbon atoms and x
 12. 4. The newcomposition of matter described in claim 1 wherein R is an alkyl groupcontaining an average of 14-15 carbon atoms and x
 14. 5. The newcomposition of matter described in claim 1 wherein said additive ispresent in an amount of about 0.75-2.0 mole percent.
 6. The newcomposition of matter described in claim 1 wherein the synthetic linearcondensation polyester is the polyester of terephthalic acid andethylene glycol, and further modified with up to about 0.45 molepercent, based on the amount of terephthalic acid, of a tetra-functionalchain-branching agent.
 7. The new comPosition of matter defined in claim6 wherein the chain-branching agent is pentaerythritol.
 8. The newcomposition of matter described in claim 1 wherein the synthetic linearcondensation polyester is the polyester of terephthalic acid andethylene glycol, and further modified with up to about 0.7 mole percent,based on the moles of the repeating unit of said polyester, of atri-functional chain-branching agent.
 9. The new composition of matterdefined in claim 8 wherein the chain-branching agent is trimesic acid.10. The new composition of matter defined in claim 6 wherein thechain-branching agent is pentaerythritol, in an amount of about 0.2 molepercent, based on the weight of terephthalic acid.
 11. The newcomposition of matter defined in claim 8 wherein the chain-branchingagent is trimesic acid in an amount of about 0.5 mole percent based onthe weight of the terephthalic acid.